Low-molecular-weight heparins are more selective for which factor?

Study for the Anticoagulation and ACS Exam with tailored flashcards and multiple choice questions, each featuring hints and detailed explanations. Prepare effectively and ensure success on your exam with confidence!

Multiple Choice

Low-molecular-weight heparins are more selective for which factor?

Explanation:
Low-molecular-weight heparins exert most of their anticoagulant effect by enhancing antithrombin III’s inhibition of Factor Xa. The shorter chains in LMWHs are effective at helping ATIII block Factor Xa, but they are often too short to form the required bridge with thrombin (Factor IIa). Inhibiting thrombin needs a longer heparin chain to link antithrombin III to thrombin, which is less common with LMWHs. So the anti-Xa activity is favored over anti-IIa activity, making LMWHs more selective for Factor Xa. Factor Xa sits upstream in the generation of thrombin, so suppressing Xa markedly reduces thrombin production and clot formation. The other factors listed are not the primary targets of LMWHs.

Low-molecular-weight heparins exert most of their anticoagulant effect by enhancing antithrombin III’s inhibition of Factor Xa. The shorter chains in LMWHs are effective at helping ATIII block Factor Xa, but they are often too short to form the required bridge with thrombin (Factor IIa). Inhibiting thrombin needs a longer heparin chain to link antithrombin III to thrombin, which is less common with LMWHs. So the anti-Xa activity is favored over anti-IIa activity, making LMWHs more selective for Factor Xa. Factor Xa sits upstream in the generation of thrombin, so suppressing Xa markedly reduces thrombin production and clot formation. The other factors listed are not the primary targets of LMWHs.

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